Monarchs feed on members of the milkweed family, and they love the Mexican Butterfly Weed--so much so that on a visit to local nurseries---all the Asclepias_curassavica in five gallon cans had stripped branches. ( I was there because they had eaten all the leaves on the ones I had). The plants are not really damaged, as the leaves promptly grow back when the caterpillars go into their next stage of becoming butterflies. Meanwhile
don't hurt the caterpillars--they are not interested in anything but milkweed, and don't have anything to do with treated plants of Asclepias_curassavica. Those will poison the caterpillars. Result: no Monarchs. These butterflies are a challenged species in So Cal where we keep cutting down the Eucalyptus groves where they gather.
Passionflower is the host for the Gulf Fritillary. (see blog for 7/19/10) which breeds and hatches earlier than the Monarch.The brightly colored caterpillar is toxic to birds. The passionflower vines have completely recovered from being the host plant for the Fritillaries.
I'm hoping the the Anise Swallowtail will take a fancy to the fennel planted especially to appeal to him. So far the fennel is flourishing madly (turns out to be delicious grilled) but no Swallowtail caterpillars so far. Stay tuned. If you plant the right plants they will come! Just haven't got the right stuff for swallowtails--they really prefer wild anise to anything else.Picky, picky, picky!